Electric circuit breaker



Oct. 25, 1938. w. E. PAUL ELECTRIC CIRCUIT BREAKER 2 Sheets-Sheet 1Filed May 17. 1938 Inventor: Willi am E. paul,

His

Oct..25, 1938. w E, PAUL ELECTRIC CIRCUIT BREAKER- Fled May 1'7, 1938 2Sheets-Sheet 2 m, UM im ...E W m Patented ocr. 2s, 193s UNITED STATESELECTRIC CIRCUIT BREAKER.

William E. Paul, Schenectady, N. Y., assignor to General ElectricCompany, a corporation ofY New York Y Applicationguay 17, 193s, serialNo. 208,392

14 Claims.

My invention relates to electric circuit breakers of the fluid blasttype wherein are pressure generated upon opening of the circuit isutilized-.to produce'azi arc-extinguishing fluid blast.

Heretofore, diiiiculty has been encountered in designing a circuitbreaker of the aforesaid type to interrupt satisfactorily currentsranging from a few amperes to those of short circuit proportions. Thisis due to the great variation of arc pressure at different currentvalues for a given length of arc, such as in the case of a high voltagepower circuit breaker of the Well-known oil blast type. In order toproduce an effective arcinterrupting blast, the arc pressure at. lowcurrents must be utilized to maximum/advantage. At high currents,however, the 'pressure may be dangerously high unless the arcg chamberis instantly vented or the arc is restricted as to length.

Various solutions to this problem have been :0 proposed includingcontrol initiated by the arcgenerated pressure. However, in view of the-high opening,- speeds. now required in practice, it is' highlydesirable that the arc pressure be anticipated ratherA than allowed todevelop before z5 initiation o1 control. Other methods have also beenproposed such as, -for example, short circuiting part of the arc in caseof heavy currents, and conversely looping and lengthening the are in thecase of weak currents. However, these 5o methods are not alwayspractical and satisfactory for particular operating requirements.

In accordance with my invention excessively high arc pressures areanticipated by lectromagnetic meansresponsive to the magnitude of thecurrent to be interrupted. More particularly, the circuit breakerfunctions normally at, low current values for developing suiiicientarcpressure to interrupt'arcing, whereas at high or short circuit currentsthe pressure-generating arc is automatically shortened by utilizingelectromagnetic forcesin the circuit that is yto be interrupted formoving an electric conductor, which may form part of the contactstructure, with respect to the arc path. With this' arrangementexcessively high arc pressures are anticipated since the control isindependent of the time of contact separation and solely dependent onthe magnitude of the current to be interrupted.

My invention will be more fully set forth in the following descriptionreferring to the accompanying drawings, and the features of noveltywhich characterize my invention will be pointed out with particularityin the claims annexed to and forming a part of this specication.

Referring to the drawings. Fig. 1 is an eleva- (cl. zoo-iso) tionalview, partly in section, of an electric circuit breaker of the oil blasttype embodying my invention; Fig. 2 is an enlarged sectional wew of thearc control contact structure shown by Fig. 1; Fig. 3 is an elevationalview in perspec- 5 tive, partly in section, illustrating another form ofmy invention; Fig. 4 illustrates an arc control contact structureparticularly suitable for circuit breakers having a wide interruptingcapacity, Fig. 5 is a fragmentary view of another form ci w arc controldevice embodying my invention, and

Fig. 6 is a partly sectional view of an are control device employing theinduction principle also embodying my invention.

The circuit breaker illustrated by Fig. i is of the 1g well-known oilblast type and .comprises a steel pressure' confining casing i withinywhich is mounted relatively movable contact structure including a xedcontact structure .2, movable contact 3, and intermediate gate contacts4. The 20 contact structure is oil-immersed as indicated. Theintermediate contacts are mounted on an insulating baiiie structure 5forming Within the casing i a lower arc chamber 6 and an upper exhaustchamber l. The baffle structure 5 is pro- 25 vided with a.` transversepassage 8 interconnecting the chambers 6 and 'l` and also intersecting alongitudinal bore 9 through which the movable rod contact 3 operates.The conducting gate contacts 4 are, normally biased by springs 4' to 30close the bore 9 at its lower end when the contact Y. 3 has moved pastthe gates toward the open circuit position. In the closing operation thecontact 3 simply biases the gates apart and moves through the bore 9into the arc chamber 6 to 35 engage the ilxed contact structure 2. Thecircuit breaker structure so far described forms no part of my presentinvention and is described in detail and claimed inv my U. S. Patent No.1,947,224 for Circuit interrupting apparatus, 40 granted February 13,1934.

\ In the operation of this breaker, a pressuregenerating arc is formedbetween the xed contact structure 2 and the intermediate or gatecontacts 4, the pressure generated within the 45 oil-filled chamber 6being utilized to create an arc-extinguishing blast through the passage8 transversely of the arc between the gate and movable contacts when thecontact structure is in the position illustrated.

Where the length of the pressure-generating Yarc in the chamber 6 issubstantially xed, it will be apparent that although thebreaker may workwell on low or medium currents, for example, the pressure generated inthe case of 55 the fixed structure along the path of thepressuregenerating arc.

Referring more particularly to Fig. 2, which illustrates the ilxedcontact structure 2 in section and in greater detail, the main contactsupport comprises a conducting frame II that is suitably expanded at itslower end, as illustrated in Fig. l, into good electrical contact withthe terminal portion I of the steel casing I. The

support I I can be generally in the form of a cylinder open at oppositeends and has'mounted thereon an arcing ring I0 which is provided with acylindrical depending extension I2 serving as a carrier for thesegmental contacts I3 coacting with the rod contact 3. The segmentalcontacts I3 are suitably biased in a well-known manner into contact withthe rod 3 by garter springs I3 and are electrically insulated at I5 andI3 from the conducting carrier I2. The segments, however, areelectrically connected byflexibleP leads Il to the lower end only of thecarrier for .the purpose presently described.

The arcing ring I0 and carrier I2 constitute a unit that is adapted forrelative movement with respect to the frame II. 'I'he unit is normallybiased to its position shown within the frame by a helical spring I8seated between an annular insulating abutment I3 secured to the frame IIand an insulating collar 23 secured to the lower end of the carrier I2.The carrier unit is limited as to vertical movement by a lower abutment2| and an upper abutment 22 forming part of the frame coacting with theinsulating collar 23. The conducting frame II and the arcingring I3 areelectrically interconnected by looped flexible conductors 23 designed topermit movement of the arcing ring between the upper and lower limitspreviously described. i

In the closed circuit position shown (Fig. 2), the circuit from theterminal of the movable contact 3 to the terminal formed Vby the casingI i's completed through the rod contact 3, segmental contacts I3,electrical connections I1, conducting carrier I2 and arcing ring I3,conducting loops 23, and conducting frame II. It will therefore be notedthat the circuit includes a loop at the conductors 23 that can expand,carrying with it the arcing ring I3, when current of predeterminedmagnitude iiows through the circuit. Since the arcing ring I3 is at alltimes electrically connected to the ilxed'contact structure 2, movementof the carrier I2upwardlyagainst the bias of spring I3inresponsetoelectromagnetic force of large currents automaticallyshortens the arc distance between the intermediate contacts 4 and thefixedl structure 2. The pressure-generating arc is correspondinglydecreased in length.- and it will be apparent that the spring tension atI8 and the design of the conducting loops 23 may be so chosen that thepressure-generating arc has a definite and predetermined length forv agiven current owing through the breaker. With this arrangement thebreaker can be designed so that the normal arc length at low currents issufilcient for arc interruption, and in the case of higher currents thearc can be automatically shortened to la point comparatively `close tothe intermediate contact structure 3 as illustrated in the dotted lineposition shown in Fig. 1.

It will also be noted that the circuit includes another loop formed bythe segmental contacts I3, flexible conductors I1 and the cylindricalcarrier I2. In this case the expanding iorc of' the loop tend, in thecase of heavy currents, to bias'the segments I3 into good `contactengagement with the rod contact 3 for minimizing heating due to contactresistance. Thiais an obvious advantage, particularly where the normalcurrent rating of the breaker is high. In the case oi' arc interruptionthe added friction between the segments I3 and rod contact 3 may causethe rod contact to. carry with it the arc control unit. However, whenlits upper limit is reached the contacts separate and if the current issumciently high, the unit will remain in its shortarc position;otherwise, the spring I3 will retract the unit to an extent depending onthe arc current. Therefore, the arc pressure is anticipated in any case.

Referring to Fig. 3 there is illustrated a comparatively-compact fixedcontact unit arranged generally to function in the manner of Fig. l.

structure is essentially the same and the fixed contact structurelikewise has several similar features. 'Ihe contact support as in theprevious case is expanded at 23, such as by a pin wedge at 23', intogood contact engagement with the steel casing I,'and an arcing bell 23having a depending cylindrical carrier 21 for the contact segments (notshown) is mounted, as in the case of Fig. 2, for relative movement inthe frame 23. Secured and electrically connected at 23 to the conductingframe 23 is a discontinuous ring 23 also connected at 33 by a flexiblelooped conductor 'to a counter or second discontinuous ring 23'. Thering 23 is secured and electrically connected to the bell 23 only at 3|so that the ring-like conductors 23 and 23' together with the flexibleconductor 33, form a loop that is bent around the longitudinal axis ofthe arcing bell 23.

The arcing bell 23 and carrier-21 are suitably biased by a spring (notshown) to a retracted position within the frame as in the case of Pig.2, the spring being omitted in the interest of clearness.

In the operation of the device, the pressurel generating-arc, as in 'theprevious case, is formed' between the arcing bell 23 and theintermediate contact structure 3. The path of the are current throughthe nxed contact structure is as indicated by the directional arrows,the current flowing from the arcing bell 23 through the ring 23' in aclockwise direction as viewed, and through the flexible conductor 33 incounterclockwise direction through the counter ring 23 which ismechanically and electrically connected to the fixedconducting contactsupport 2l. The segmental contacts (not shown) can if desired beconnected in the circuit in-the manner shown in Fig. 2.

When Athe breaker is opened the electromagnetic repulsion between therings 23 and 23' due to the opposing directions of the current pathscauses extension of the arcing unitl (23, 23' and 21.) in an upwarddirection tending to shorten the arc to an extent depending on themagnitude of the arc current. This arrangement is obviously more compactthan that of Fig. 1 since the,

loop for utilizing the electromagnetic forces of vic the circuit isconcentrically disposed with respect to the arc and in etfect bent backupon itself, as contrasted with the laterally extending loops 23 ofFigs. 1 and 2.

'I'he arrangement shown by Fig. 4 is particularly adapted to utilize tothe maximum extent the electromagnetic forces involved in a circuit loopassociated with the movable arcing member. To this end therelativelymovable arcing member 34, which may also constitute thecontact structure, is electrically connected at 35 to an insulatedconductor I36 that is normally arranged in a ilattened double loop andconnected at its ether terminal at 31 to the conducting expanding ring31' corresponding in function to the expanding ring 25 of Fig. 3. Themovable arcing member t4, which can be suitably formed as a socketcontact, for example, for coacting with the contact tip of the movablerod 3 is mounted for limited reciprocal movement with respect to aninsulating cylinder 38 having a central bore 38 within which a guideextension 39 of the movable member 34 is disposed. The insulatingcylinder 38 is xed within the expanding ring 3l'. The extension 39 isresiliently biased by a helical spring 39' toward the retracted positionshown. Accordingly, when current traverses the breaker the insulatedlooped conductor 36, which is suitably secured at one point to themovable arcing element 34, such as by a clip member 38', tends to expandso as to icrm a circle. Expansion of the loop is opposed by the spring38' which is selected as in the previcus case in accordance with theoperating re- Imiiiements of the breaker.

'he insulated conductor 36 can obviously form any desired number ofloops in order to meet the particular design requirements of thebreaker. For example, where lateral space is restricted, the number cicoils can be increased. The conductor loops are also preferably designedso that l the arcing member 34 is at the position of minimum arc lengthwhen the loop is in the form of a substantially complete circle. 'Withthis arrangement the electromagnetic forces acting on the loops aresubstantially dissipated iii/hoop tension and the movable arcing unit isaccordingly not subjected to high mechanical stresses when in the,position of minimum. arc length. When the circuit is interrupted the'spring 39' returns the arcing member 3l to its initial retractedposition where it remains in they case ofv arc-'regulating operation ofthe arcing member. v

This is overcome according to my invention by applying theelectromagnetic forces to the arcing member so that it moves along withthe movable contact until it reaches itsregulating position asdetermined by the-magnitude of the arc current. in other words,thecontrol anticipates` excessive arc pressure due to a long, heavycurrent arc.

Fig. illustrates a simplified arrangement wherein the nxed segmentalcontacts 4l! coac\t with the rod contact 3 in the manner abovedescribed, the segmental contacts being suitably mounted within aconducting support 4| that is electrically connected to a terminal ofthe breaker. The relatively movable arcing ring 42 is in the presentinstance pivotally mounted with respect to the support 4I by means of anarm 43 5 pivotally connected at 44 to a conducting exten- `sion 45 ofthe contact. carrier. A spring 46 functions to keep the arcing ringnormally in the retracted position shown, and a stop member 45' iixed tothe support 45 serves to limit movement inthe opposite direction.

The conducting loop. in the present instance for' controlling thepositionA of the arcing ring is formed by the conducting members $3 and45 and to this end the aforesaid members are electrically connected by aflexible conductor at 41 adjacent the pivot 44 and are provided with `aninsulating spacer' 48 for preventing short circuiting of the loop. Theoperation is believed to be apparent from the above description, the arccurrent after transferring to the arcing ring 42 traversing the loop43-45 to control the position of the arcing ring in accordance with themagnitude of the arc current. This design is comparatively simple inthat the breaker in the closed circuit position utilizes simply theconventional contact structure, the arcing ring funci tioning only uponopening of the circuit on heavy or short circuit currents. The relationbetween arc length and arc current can readily be chosen by suitableadjustment of thespring tension at 46, and also by changing thedimensions of the loop i3-4B.

In the arrangement shpwn byFig. 6, the induction principle is employedfor the purpose of simplifying the structure in certain cases and fortact 3. 'In the present case the fixed contact 52 is-.mounted within astationary insulating cylin- 5o der 53 that'is secured to the switchcasing in any suitable manner, the cylinder being provided with lateralanges 53' for positioning the arc control means.

The movable arcing member for decreasing the arc length in accordancewith the magnitude of the current comprises in the present instance aconducting sleeve 54 of copper or the like mounted around andconcentrically of thev insulating cylinder 53. The sleeve 54 is biasedby a spring 55 seated on the upper flange 53 of the fixed cylinder 53toward a retracted position with respect to the arc path, and asshowrris in the maximum arc length position. For the purpose ofrelieving gas pressures and eliminating piston eil'ect, the sleeve 54isprovided with apertures54'.

When current of predetermined magnitude traverses the series coil 5lcurrent is induced in the conducting ring 54, which forms in effect a inopposite directions establish a repellant force tending to raise thering 5,4 against the bias of spring 55 to the arc-controlling positionrequired.

The are lsthereby bridged in part, the total arc length then comprisingthe two short arcs formed between the rod 3 and ring 5l, and the ring Iland ixeo'; contact 5t.

Accordingly; the arc pressure is anticipated even before separation ofthe contacts, since the It should be understood that my invention is notlimited to specic detalls of construction and arrangement thereof hereini11ustrated,"a.nd` that changes and modications may occur to one skilledin the art without departing from the spirit of` my invention.

l ated uid blast type comprising separable contact structure betweenwhich a pressure-generating arc is formed upon opening ofthe circuit, anarcing member movabie with respect to one of the contacts, andelectromagnetic means con- V, trolied by the arc current for causingmovement of, said arcing member into the arc patliso as to decrease thelength of said arc to an extent depending on the' magnitude ofthe arccurrent.

3. en electric circuit breaker of the arc-generuid blast type comprisinga pair of rele.u "rely movable contacts between which an arc is formedupon opening of the circuit, contact structure positioned intermediatesaid contacts in the open circuit position thereof, an arcing memberassociated one of 'said contacts, said arcing member movable beyond saidcontact 'tctrard said intermediate contact structure and into the arcpath, and electromagnetic means ccntroed by the arc current for causingmovement of said srcirig member so as to decrease the length of the arcbetween said arcing member and intermediate contact structure te ar.extent depending on the magnitude of the are current.

.en electric circuit breaker of the arc-generated biast type comprisingseparable contact structures between which an arc is formed upon cpenngof the circuit, an arcing member eiectrcail; connected to and movablewith respect cc the contacts and electromagnetic means by the arccurrent prior to separation said contact structure for moving saidarcing member with respect tc the arc path so as to decrease the lengthof said arc tc an extent depending on the magnitude of the arc current,said eiectromegnetc means tending tc initiate the movement of saidarcing member at the um stent overload occurs `whereby generation ofexcessiye src pressure is anticipated.

en electric circuit breaker of the arc-generated bias; type comprising afixed contact a ccactin'g movable contact, an arcing member mounted onsaid fixed contact for reciprocal -rectilinear movement with respectthereto, said said member towards a retracted position with respect tosaid arc path and exlble conducting means interconnecting said memberand xed contact forming a loop for moving said arcing member into thearc path to an extent depending on the magnitude of the arc current.

6. An electric circuit breaker ot the fluid blast type comprisingrelatively ilxed, movable and intermediate contact structures arrangedso that the arc pressure generated between said intermediate structureand one of said other structures tends to interrupt the circuit, and arccontrol means for the pressure generating arc including an arclng membermovable with respect to one of said contact structures into the arcpath, and electromagnetlc means for biasing said arcing member into thearc path for shortening said arc to an extent depending on tbe magnitudeof the arc current. I

7. An electric circuit breaker of the arc-generated iluid blast typecomprising a xed contact and a relatively movable contact between whicha pressure-generating arc is formed upon separation of said contacts,arc control means mounted for relative movement with respect to saidfixed contact comprising an arcing ring movable between said fixedcontact and a position beyond the same into the arc path, means biasingsaid arcing ring towards a retracted position with respect to said path,contact means for coacting with said movable contact carried by andmovable with said arcing member, and iiexibie conducting meansinter-connecting said fixed contact structure and said arcing ring, saidconducting means being formed as a loop so that the electromagneticforces of the arc current tend tc bias said arcing ring into the arcpath to an extent depending on the magnitude of the arc current.

8. An electric circuit breaker of the arc-generated fluid biast typecomprising ised contact structure and a coacting movabie Contact,control structure mounted for reiatve movement with respect to said nxedcen-tac; structure comprising an arcing ring adapted tc coaci'. withsaid movable contact, a contact ce.L ler secured to and dependingrfromsaid arcing ring, a plurality of contact elements mounted in saidcarrier for engagement with said movable contact, means electricallyconnecting said contact eiements to said carrier oniy at one endthereof, means eiectrically connecting the opposite end of'said carrierat said arcing ring to said fixed contact structure, said means forminga loop arranged sc that said arcing ring is biased into the arc path toan extent depending on the magnitride of the arc current traversing saidloop, said contact -lcments being likewise biased into contactengagement with said movable contact in e. similar manner, and springmeans for biasing said arcing ring and contact carrier towards aretracted position with respect to said arc path,

9. An electric circuit breaker of the arc-generated fluid bast typecomprising xed and movabe contact structures, arc control meansassociated with said Sxed structure including a conducting member in theform of a discontinnous ring, said ring being eiectrically and rigidiyconnected at one end to said'iixed structure, a relativeiy movabiediscontinuous ring generally similar to said first ring in superposedposition with res t to said rst ring, flexible conduct ing meansinterconnecting the free end of said first ring and one end of saidsecond ring, contact means including an arcing member mounted formcement with said second ring, said said fixed contact structuretraverses said rings in opposite directions whereby said arcing memberis biased into the arc path to an extent de` pending on the magnitude ofthe arcflcurrent, and resilient means for biasing in the oppositedirection said arcing member. 10. An electric circuit breaker oi thearc-generated fluid blast type comprising relatively vmovable contactstructure between which a pressuregenerating arc is formed uponseparation of said contact structure, are control means associated withone of said contact structures comprising an arcing member adapted tomove into the path of said arc for decreasing the length thereof, andelectromagnetic means for controlling the position of said arcing memberin said path to an extent depending on the magnitude of the arc currentcomprising conducting means interconnecting said contact structure andsaid arcing member, said conducting means forming a current path in theshape of a compressed loop that is positioned substantiallyeoncentrically with respect to said arcing member. 11. An electriccircuit breaker of the arc-generated iiuid blast type comprisingrelatively movable contacts between which a pressure-generating arc isformed upon separation thereof, one of said contacts including arelatively movable arcing member adapted to move into the are path fordecreasing the length of said arc, and a flexible conductorinterconnecting said con- I tact and arcing member, said conductor beingformed as a coil so that' arc current traversing said conductor tends tomove said arcing member into the arc path to an extent depending on themagnitude of the arc current whereby the 40 minimum arc length positionis attained when said conductor assumes a generally circular form.

12. An electric circuit breaker of the arc-generated fluid blast typecomprising fixed and movable contact structures, arc control meansmounted for relative movement with respect to said fixed structurecomprising an arcing member, aS flexible conductor normally formed as acompressed coil having a plurality of turns electrically interconnectingsaid fixed structure and arcing member, said coil being mechanicallyconnected at one terminal to said arcing member whereby expansion ofsaid coil due to passage of arc current therethrough tends to move saidarcing member into the path of the arc for decreasing the lengththereof, and means resiliently biasing said arcing member in theopposite direction, the minimum arc length position of said arcingmember being determined by the fully extended position of said coilwhereby the electromagnetic stresses at high currents are substantiallydissipated in hoop tension.

13. An electric circuit breaker of the fluid blast type comprisingseparable contact structure between which a pressure-generating arc isformed upon opening of the circuit, and arc control means associatedwith one part of said contact structure including a conducting `\arcingmember movable with respect to said part into the are path, means forresiliently biasing said member towards a retracted position withrespect to said arc path, and means traversed by the arc current relatedto said arcing member so that said arcing -member is repelled bymagneticv forces into the arc path to an extent depending on themagnitude of said arc current. 14. An electric circuit breaker of thefluid blast type comprising separable contact structure between whichapressure-generating arc is formed l upon opening of the circuit, amovable arcing member forming a short-circuited conductor,

means resiliently biasing said arcing member toward a retracted positionwith respect to the are path, and means traversed by the arc currentassociated with said contact and inductively related to said arcingmember, said arcing member being. repelled into the arc path by theresulting magnetic forces to decrease the length of the arc to an extentdepending on the magnitude of the arc current.

WILLIAM E. PAUL.

